Previous comparisons of solar energetic particle (SEP)
events at 1 AU with associated coronal mass ejections (CMEs)
have shown a correlation between peak SEP fluxes and CME
speeds. These results have provided some of the evidence
for acceleration of SEPs by CME-driven shocks. We compare
SEP observations from the Helios spacecraft with associated
CME and shock speeds reported by Sheeley et al. (JGR, 1985).
We find that the 3 < E < 6 MeV peak proton fluxes correlate
better with the in situ shock speeds than with either the
CME speeds or the average transit speeds of the shocks.
This establishes a closer physical connection between SEPs
and CME-driven shocks than the previous work which used
CME speeds as rough proxies for the shock speeds. We also
examine the speed profiles of a number of fast CMEs observed
with the SOHO LASCO coronagraph to look for distinguishing
characteristics of CMEs associated with SEPs at 1 AU.